To meet different power specifications of numerous electronic products, various electronic modules, such as power adapters, power transformers and power connectors, have been provided in the art. Such an electronic module has a housing formed by upper and lower shells to isolate interior electronic elements from exterior dust or vapors. However, such shells do not have a joint sufficient to stop fluid flowing into the housing. In other word, such an electronic module is not waterproof. Further, the joint mechanisms used for the shells adversely affects not only appearance of the electronic module, but also the entire structural strength and electrical characteristics thereof. Therefore, it is important to provide an electronic module with shells having a proper joint mechanism that is waterproof.